1. Field of the Invention
The present invention relates to a light amount adjustment apparatus for use in optical apparatuses such as a photographing apparatus, a manufacturing method of the apparatus, and such a photographing apparatus, particularly to a diaphragm apparatus which is a light amount adjustment member and in which an optical filter is integrally disposed in a so-called diaphragm blade.
2. Related Background Art
In a related-art diaphragm apparatus, a diaphragm blade which is a light amount adjustment member is used to adjust a passed light amount. Moreover, particularly with respect to a high-luminance subject, a diaphragm diameter is not reduced very excessively and is set to a constant diaphragm diameter to prevent a resolving power from being deteriorated by diffraction. Instead, optical filters such as a neutral density filter (hereinafter abbreviated as the ND filter) are used to limit the passed light amount, and thereby an image quality is prevented from being deteriorated.
Concretely, various diaphragm apparatuses have been proposed in which the ND filter is not attached to the diaphragm blade and which are constituted to have an optical function in an independent state. Alternatively, the diaphragm blade is provided with the ND filter by attaching the ND filter which is a member separate from the diaphragm blade to a part of the diaphragm blade with an adhesive. In this constitution, when the subject has a high luminance, the diaphragm diameter is not reduced very excessively, and an diaphragm aperture is maintained at a constant size. Instead, the passed light amount is limited so that the ND filter is positioned on an optical axis.
However, with the diaphragm blade constituted to be a member separate from the ND filter, there are disadvantages that positional shift is generated during the attaching of the ND filter to the diaphragm blade and there is no degree of freedom in the shape of the ND filter. Therefore, for a purpose of improving this, a diaphragm apparatus has been proposed in which the diaphragm blade is constituted integrally with the ND filter (see Japanese Patent Application Laid-Open No. 07-104343) The constitution is shown in FIG. 10.
In FIG. 10, reference numeral 903 denotes a diaphragm blade driving lever which is attached to a shaft of a motor (not shown) via a hole 903a and which can reciprocate/rotate centering on the hole 903a. Reference numerals 901 and 902 denote first and second diaphragm blades including grooves 901a and 902a into which projecting pins 903b and 903c on opposite ends of the diaphragm blade driving lever 903 are fitted so as to be relatively slidable. Reference numerals 901c and 902c denote aperture edges of the diaphragm blades. Reference numerals 904a and 904b are ND filters which are integrally constituted of the same members as those of the diaphragm blades 901 and 902 in the present invention. That is, the ND filters 904a and 904b are constituted so as to have a constant transmittance, and light is blocked in another region.
Moreover, the diaphragm blades 901 and 902 are moved in directions reverse to each other along an arrow f direction, when the diaphragm blade driving lever 903 reciprocates/rotates centering on the hole 903a. As a result, the ND filters 904a and 904b close/open a light path hole 906 formed through a base plate (not shown). That is, when the ND filters 904a and 904b are positioned in the light path hole 906, the passed light amount is attenuated, and the light amount incident upon an image pickup device (not shown) is adjusted. It is to be noted that in edges of the diaphragm blades 901 and 902, grooves 901b and 902b are formed in parallel to a movement direction of these blades. Guide pins 905 projecting from the base plate (not shown) are inserted in these grooves so that the pins can slide with respect to one another.
However, the above-described related art has a room for improvement as follows. That is, in Japanese Patent Application Laid-Open No. 07-104343, the constitution in which the diaphragm blade is constituted integrally with the ND filter is disclosed. It is also disclosed that a silver halide photosensitive material (silver halide film) is used as the material of the diaphragm blade. However, a detailed manufacturing method is not disclosed. Moreover, according to the present inventors' study, with the use of the silver halide film in the material forming the ND filter, a light flux passed through the film is largely scattered, and therefore there is a problem that the resolution of the image is deteriorated.